Modification of the photoconducting properties of ZnO thin films via low-temperature annealing and air exposure

BRIDOUX, G.; VILLAFUERTE, M.; FERREYRA, J.M.; RUANO, G.D.

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Año: 2020 vol. 33

0953-8984

A simple thermal annealing at 150 C followed by exposure to air ambient conditions in epitaxial ZnO thin films produces a photoconductivity enhancement and a reduction of the energy gap. The first effect is related to a release of carriers from bulk traps while the second is caused by a gradual adsorption of species on the film surface which increases the band bending, as x-ray photoemission spectroscopy (XPS) shows. An observed drift of the photoconductivity and the energy gap over the days is connected to this adsorption kinetics. These findings have a potential application in ZnO based optoelectronic devices.